Gas-operated automatic firearm having thermal firing rate control

ABSTRACT

A gas operated automatic firearm having a breech casing with a cylindrical chamber and a barrel having a gas passage communicating with the cylindrical chamber. A piston is in the chamber and an insert closes one end of the chamber. Means guide the combustion gas from the passage into the chamber at the end nearest the piston. Such means guide the gas along a path extending first towards the end of the insert remote from the piston and then guide the gas to the end of the insert adjacent the piston. Such guiding means are grooves and bores in the insert.

[451 Sept. 12, 1972 GAS-OPERATED AUTOMATIC FIREARM HAVING THERMAL FIRING RATE CONTROL Inventors: Ernst Muhlernann, Bruun; Jean Eskild, Zurich, both of Switzerland Werkzeugmaschinenfabrik Oerlikon-Buhrle AG, Zurich, Switzerland Filed; June 20, 1970 Appl.No.: 50,144

Assignee:

us. Cl ..89/193 Int. Cl ..F41d 5/08 Field of Search ..89/191, 192, 193

[56] References Cited UNITED STATES PATENTS 2,872,851 2/1959 Katz ..89/193 Primary Examiner-Stephen C. Bentley Attorney-Wenderoth, Lind & Ponack ABSTRACT A gas operated automatic firearm having a breech casing with a cylindrical chamber and a barrel having a gas passage communicating with the cylindrical chamber. A piston is in the chamber and an insert closes one end of the chamber. Means guide the combustion gas from the passage into the chamber at the end nearest the piston. Such means guide the gas along a path extending first towards the end of the insert remote from the piston and then guide the gas to the end of the insert adjacent the piston. Such guiding means are grooves and bores in the insert.

3 Claims, 3 Drawing Figures fi /5 I0 I36 123727189 PATENTEIJSEPIZIHYZ V I 3,690,219

Fig.2 1

INVENTORS ERNST MUHLEMA N N JEAN ESKILD BRUUN Attorneys GAS-OPERATED AUTOMATIC FIREARM HAVING THERMAL FIRING RATE CONTROL The invention relates to a gas-operated automatic firearm comprising a barrel having with a gas-passage communicating with a cylindrical chamber containing a piston and an insert defining one end of the chamber and also allowing gas to pass from said gas passage to the interior of the chamber.

In a conventional automatic firearm ofthe above type the insert forms a plug which tightly seals the cylinder and which is formed with an internal projection that in conjunction with the internal wall of the cylinder defines an annular channel for the passage of the gases therethrough. Between the plug and this projection is an annular groove into which the gas passage discharges the gas. The annular groove communicates with the cylinder chamber in front of the piston not only through the annular passage but also through bores that obliquely traverse the projection.

In this conventional arrangement the gas passage is located far to the rear in the barrel and thus enters the cylinder near the piston. In order to unseal the breech at the required instant this location of the gas passage is essential. In a conventional firearm of this type this means that the length of the path becomes very short and this has the adverse effect of accelerating the firing I rate when the firearm becomes hot. In order to suppress this effect a thermal rate control is provided which operates by constricting the annular gas passage when the temperature of the firearm rises. However, this control is very sluggish in action. It does not become effective until after prolonged continuous fire when the firing rate has already appreciably risen.

The present invention aims to overcome these drawbacks. Despite the location of a gas passage far to the rear in the barrel the arrangement of the invention permits the length of the gas path to be greatly extended and thus a rise in the firing rate to be avoided.

A gas operated firearm according to the invention comprises a gas operated automatic firearm comprising a barrel having a gas passage communicating with a cylindrical chamber containing a piston and an insert defining one end of said chamber and allowing gas to pass from said passage into said chamber at the end nearest the piston, in which the path for the gas extends first towards the end of the insert remote from the piston and then returns to the end of the insert nearest the piston.

The invention is illustrated by way of example in the accompanying drawings in which FIG. 1 is a section of a gas operated automatic firearm according to a first embodiment of the invention;

FIG. 2 is a section on the line [1-11 of FIG. 1;

FIG. 3 is a similar view as FIG. I of a second embodiment of a gas operated automatic firearm according to the invention.

With reference to FIGS. 1 and 2 the automatic firearm comprises a barrel 1 and a breech casing 2. The

breech casing 2 includes a cylindrical chamber 3 which piston 6 illustrated in FIG. 1 the head of the piston is in contact with an end face 10 of an extension of the plug 5. Inside the chamber 3 is a stack of dish springs 11 which serve as a buffer for the piston 6 and cooperate with an annular face 12 at the end of the piston 6, adjacent the piston rod 7. A hole 13 provides communication between the chamber 3 and the atmosphere.

The plug 5 has an extension towards the piston 6 forming the insert 14 which in diameter corresponds to the internal diameter of the chamber 3. The insert 14 contains two peripheral grooves 15 and a helical groove 16 milled into its circumference. The groove 16 connects the two peripheral grooves 15. The gas passage 4 from the interior of the barrel I communicates with the peripheral groove nearest the piston 6. The insert 14 is further provided with an axial blind bore 17 which extends to the end face 10, the final portion being in the divergent cone. The front end peripheral groove 15 communicates with the central axial bore 17 through four angularly equidistantly disposed channels 18 normal to the longitudinal axis of the helical groove 16, which coinsides with the axis of the plug 5.

The cross section of the grooves l5, 16 need not necessarily be a trapezium as shown in FIG. 1. It might also be semicircular, rectangular or square.

The illustrated firearm operates as follows:

When a fired projectile, (not shown), has travelled up the barrel 1 across the gas passage 4, the powder gases will pass through the passage 4 into the peripheral groove 15 in the rear end of the insert 14, and then through the groove 16 into the front end groove 15, through the radial channels 18 into the central bore 17 and thus impinge on the head of the piston 6 which together with its piston rod will thus be accelerated away from the breech casing to operate the firearm in a known manner. The front end face of the piston 6 uncovers the hole 13 when the piston reaches the end of its rearward stroke and the gas in the chamber 3 can thus escape to atmosphere. At the end of its rearward displacement the annular face 12 of the piston 6 strikes the stack of dish springs 11, braking the piston 6 and causing it to rebound towards the plug 5 where it remains until the next projectile is fired.

With reference to FIG. 3 the insert 14 which forms an extension of the plug 5 has a diameter smaller than that of the interior of the chamber 3 along most of the length. Peripheral grooves 19 are milled at regular axial intervals in the surface of the insert 14 along its entire length. Gas from the passage 4 discharges into the rearmost peripheral groove 19 nearest the head of the piston 6. The front end peripheral groove 19 communicates with a central blind bore 17 through radial channels 18. The insert 14 has an annular flange 20 equal in diameter to that of the chamber 3 at its rear end which thus seals the insert from the chamber 3.

This modified insert 14 does not affect the manner in which the firearm functions, which remains as has been described with reference to FIGS. 1 and 2.

In both embodiments the presence of the insert 14 substantially lengthens the gas path from the gas passage 4 to the piston 6, since the gas is forced by the insert first to travel away from the piston and then to return.

In the first embodiment of FIG. 1 the gases are conducted rearwards through the helical groove 16. The gas stream then divides between the four radial channels 18 before recombining in the central blind bore 17 and impinging upon the head of the piston 6.

In the second embodiment of FIG. 3 the insert 14 in cooperation with the wall of the cylindrical chamber 3 forms a labyrinth seal through which the gases flow axially along the insert 14, the cross section of flow being alternately constructed and enlarged. The division and recombination of the gases is again effected in the radial channels 18 and in the central blind bore 17.

In both embodiments friction and turbulence bring about an appreciable reduction in the pressure of the gas.

Theoretical studies and practical tests have shown that at higher temperature and consequent increasing velocity of the gas the losses in pressure rise to a sufficient extent to prevent the firing rate of the firearm from becoming significantly faster, this being exclusively due to the design of the system of gas channels through the insert.

We claim:

I. A gas operated automatic firearm comprising a breech casing having a cylindrical chamber, a barrel having a gas passage communicating with said cylindrical chamber, a piston in said chamber, an insert defining one end of said chamber having an annular flange at the end adjacent said piston equal to the internal diameter of said chamber, the external diameter of said insert apart from said annular flange being less than the internal diameter of said chamber, said insert having at equidistant axial intervals annular grooves, means guiding the gas from said gas passage over said annular grooves into said chamber at the end nearest said piston, said gas first flowing towards the end of said insert remote from said piston and then to the end of said insert adjacent said piston.

2. A gas operated automatic firearm comprising a breech casing having a cylindrical chamber, a barrel having a gas passage communicating with said cylindrical chamber, a piston in said chamber, an insert defining one end of said chamber having an annular peripheral groove at either end, said two grooves being connected by a helical peripheral groove, means guiding the gas from said gas passage through the peripheral grooves into said chamber at the end nearest said piston, the gas first flowing towards the end of said insert remote from said piston and then to the end of said insert adjacent said piston.

3. A gas operated firearm according to claim 1 in which the end of said insert remote from said piston contains radial. coplanar passages and said insert has a central blind bore extending through the length of said insert and opening into said chamber opposite the face of said piston. 

1. A gas operated automatic firearm comprising a breech casing having a cylindrical chamber, a barrel having a gas passage communicating with said cylindrical chamber, a piston in said chamber, an insert defining one end of said chamber having an annular flange at the end adjacent said piston equal to the internal diameter of said chamber, the external diameter of said insert apart from said annular flange being less than the internal diameter of said chamber, said insert having at equidistant axial intervals annular grooves, means guiding the gas from said gas passage over said annular grooves into said chamber at the end nearest said piston, said gas first flowing towards the end of said insert remote from said piston and then to the end of said insert adjacent said piston.
 2. A gas operated automatic firearm comprising a breech casing having a cylindrical chamber, a barrel having a gas passage communicating with said cylindrical chamber, a piston in said chamber, an insert defining one end of said chamber having an annular peripheral groove at either end, said two grooves being connected by a helical peripheral groove, means guiding the gas from said gas passage through the peripheral grooves into said chamber at the end nearest said piston, the gas first flowing towards the end of said insert remote from said piston and then to the end of said insert adjacent said piston.
 3. A gas operated firearm according to claim 1 in which the end of said insert remote from said piston contains radial coplanar passages and said insert has a central blind bore extending through the length of said insert and opening into said chamber opposite the face of said piston. 